As @DavidPike suggests, you can have it appear as an expression in the popup or the table in the "Classic" map. Was there a reason you needed to have a derived value as its own column?
Regardless, there is a way to automatically update it if you're comfortable with a bit of Python.
Simple Version: Frequent Intervals
So, you could just write a script like this in an AGOL Notebook:
from arcgis import GIS
# Connect to portal, get your layer
gis = GIS('your-org-url', 'user', 'password')
lyr = gis.content.get('hosted-layer-itemID')
# Calculate the field
lyr.layers[0].calculate(
calc_expression = {
'field': 'concat-fieldname',
'value': 'CONCAT(firstfield, secondfield)'
}
)
Then use the Tasks tab in the notebook to schedule it to run often enough to keep things up to date. Scheduled runs do cost you credits, but such a short, simple script will likely cost very little, even running it frequently.
Fancy Version: Injected Parameters and Webhooks
This can get quite a bit more complex (perhaps more trouble than it's worth), but will only trigger when, say, a new feature is created. Getting this to work does require your layer to be set up a certain way, so maybe this option is out of reach. But it's worth mentioning.
First, set up a notebook like above, but include a where clause in your field calculation. Set the variable where to '1=1' earlier in the notebook, then use injected parameters to allow this to be overridden.
Create a task to run at regular intervals, but leave it disabled for now.
where = '1=1'
lyr.layers[0].calculate(
where = where
...
Next, create a webhook on the hosted feature service. Define it to trigger whenever you feel it's necessary, maybe on adds and updates of features.
Now, here's the tricky part. You don't really have control over the contents of your webhook's payload so you'll need some kind of intermediary here. Lots of the Esri examples use Integromat, maybe you have Microsoft Flows / Power Automate. You could also create a totally custom program to do this, if you know what you're doing.
However you do it, have the intermediary catch the payload and get the objectID of the created feature. Then you can submit a POST request to https://kendall.maps.arcgis.com/sharing/rest/community/users/<your-username>/tasks/<your-task-ID>/update to schedule a run of your notebook.
The payload for your POST request will look something like this:
{
"title": "Single Run",
"itemId": "your notebook itemID",
"startDate": "UNIX timestamp of current time",
"type": "ExecuteNotebook",
"parameters" "{\'updatePortalItem\':true,\'saveInjectedParameters\':false,\'notebookParameters\':\'{\\\'where\\\':\\\'objectid=THEOBJECTID\\\'}\'}",
"minute": "*",
"hour": "*",
"dayOfMonth": "*",
"month": "*",
"dayOfWeek": "?",
"maxOccurrences": "1"
"f": "json"
}
You'll probably need to figure out the token portion, too.
Worth noting: you can also work with scheduled notebook tasks in Python, if that's easier for you.
Anyway, that should get your task re-set to run at the current time, just once. By piping in the created/updated objectid from the webhook, the task's "where" parameter will filter your calculation to just those features added or updated.
I've gone on long enough. Talk about using a cannon to swat a mosquito! The simple option is probably all you'd want.
- Josh Carlson
Kendall County GIS
